High density plasma chemical vapor deposition process

ABSTRACT

A method for depositing dielectric material into gaps between wiring lines in the formation of a semiconductor device includes the formation of a cap layer and the formation of gaps into which high density plasma chemical vapor deposition (HDPCVD) dielectric material is deposited. First and second antireflective coatings may be formed on the wiring line layer, the first and second antireflective coatings being made from different materials. Both antireflective coatings and the wiring line layer are etched through to form wiring lines separated by gaps. The gaps between wiring lines may be filled using high density plasma chemical vapor deposition.

This application claims priority from provisional application Ser. No.60/041,790, filed Apr. 2, 1997.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a process for forming conductiveregions such as wiring lines and for filling the gaps between conductiveregions in a semiconductor circuit with a dielectric material using highdensity plasma chemical vapor deposition.

2. Description of the Related Art

Many highly integrated semiconductor circuits utilize multilevel wiringline structures for interconnecting regions within devices and forinterconnecting one or more devices within the integrated circuits. Informing such structures, it is conventional to provide first or lowerlevel wiring lines or interconnect structures and then to form a secondlevel wiring line in contact with the first level wiring lines orinterconnect structures. A first level interconnect might be formed incontact with a doped region within the substrate of an integratedcircuit device. Alternately, a first level interconnect might be formedto a polysilicon or metal wiring line that is in contact with one ormore device structures in or on the substrate of the integrated circuitdevice. One or more interconnections are typically formed between thefirst level wiring line or interconnect and other portions of theintegrated circuit device or to structures external to the integratedcircuit device. This is accomplished, in part, through the second levelof wiring lines.

Most often, the wiring lines of the multilevel interconnect structureare formed by conventional photolithographic techniques. For example,devices such as FETs, diodes or transistors are formed in and on thesubstrate to form an integrated circuit device and a first level ofinsulating material is deposited over the device. A pattern of contactholes is defined through the first level of insulating material and, atsome point in the process, the contact holes are filled with aconducting material to define vertical interconnects through the firstlevel of insulating material to contact points of the appropriate onesof the devices on the surface of the substrate. A first metal layer thatwill be patterned to form a first level of wiring lines is provided onthe first level of insulating material and over the surface of thedevice. An etch mask is formed on the surface of the first metal layerthat defines a pattern of wiring lines to connect to various ones of thevertical interconnects. Generally, the etch mask is formed by providinga layer of photoresist on the surface of the first metal layer, exposingthe layer of photoresist through an exposure mask and developing thephotoresist to form the etch mask. Etching processes remove thoseportions of the first metal layer exposed by the etch mask, leavingbehind the desired pattern of wring lines.

Reduced design rules for forming integrated circuit devices havenecessitated the use of photolithography steppers that use shortwavelength exposure sources. Such short wavelength exposure sourcesallow for finer resolution lithography, but have the drawback of muchhigher levels of reflection from different components of the integratedcircuit device. For example, during exposure of the photoresist mask, itis possible that light may pass entirely through the photoresist andreflect from the surface of the first metal layer back into the lowerportions of the photoresist layer. To the extent that the reflectedlight is scattered by the surface of the first metal layer, it ispossible that unwanted portions of the photoresist layer might beexposed. These unwanted reflections could undesirably narrow the firstlevel metal wiring lines formed in this process.

It is desirable for the wiring lines and gaps between the wiring linesto be formed as accurately as possible. Misalignment or improperthickness of the developed photoresist protective layer may cause lightto be reflected from the surface of a metal layer back up to thephotoresist layer, exposing portions of the photoresist layer that areintended to not be exposed. Such additional exposure from lightreflecting from the underlying metal layer may cause the developedportion of the photoresist layer to have a larger width than intended,which means that a narrower than intended surface area will be etchedand the wiring lines may be too close together, leading to undesirablecapacitive coupling or even shorting between lines. In addition, lightreflected from the underlying metal layer may cause portions of thephotoresist layer to be thinner than intended, which may result in thethinner portions being etched through and the underlying metal layer,which should be protected by the photoresist, will be partially etched.Such partial etching may form voids in the wiring lines and lead todecreased device performance and/or failure. The use of photoresistmasks can also lead to contamination from the photoresist, such ascarbon compounds, being deposited in the gaps between wiring lines or onthe wiring lines and forming defects that interfere with processing andultimately hinder device performance.

As devices are scaled to smaller geometries, the gaps formed betweenwiring lines generally have high aspect ratios (ratio of height towidth) which are harder to fill with dielectric material than smallaspect ratio gaps. In addition, as the distance between wiring lines andother conductors becomes smaller, capacitive coupling between wiringlines and other conductors becomes a limitation on the speed of theintegrated circuit device. For adequate device performance in reduceddimension devices, it is necessary that the lithography and etchingsteps be accurately carried out to ensure proper location and sizing ofthe wiring lines and gaps. It is also necessary that the dielectricmaterial subsequently deposited into the gaps between wiring lines meeta number of requirements. The dielectric material should be able tocompletely fill the gap between conductors and should be planarizable sothat successive layers can be deposited and processed. The dielectricmaterial should also be resistant to moisture transport and have apredictable and low dielectric constant to minimize capacitance betweenadjacent wiring lines and between wiring lines on different layers.

It is thus important to accurately form the wiring lines and gaps, andto deposit a high quality, substantially void-free dielectric into thegaps. Dielectric layers for wiring line isolation are often formed bychemical vapor deposition (CVD) processes, which deposit material onto asurface by transporting certain gaseous precursors to the surface andcausing the precursors to react at the surface. Common CVD methodsinclude atmospheric-pressure CVD (APCVD), low-pressure CVD (LPCVD) andplasma-enhanced CVD (PECVD). High quality APCVD and LPCVD oxides may bedeposited at high temperatures (650-850° C.), but such temperatures aregenerally not compatible with preferred wiring materials such asaluminum. Lower temperature APCVD and LPCVD processes tend to yieldoxides that are comparatively more porous and water absorbing and thatmay be poorly suited to use as intermetal dielectrics. Acceptable oxidesmay be formed using PECVD processes, which use a plasma to impartadditional energy to the reactant gases. The additional energy suppliedby the plasma enables PECVD processes to be carried out at lowertemperatures (approximately 400° C. and less) than APCVD or LPCVDprocesses.

One known method for depositing dielectric material between wiring linesforms a sandwich of a layer of silane-based or TEOS-based oxidedeposited by PECVD together with a layer of spin-on-glass provided inthe gaps and over the wiring lines. Another method deposits only aTEOS-based dielectric layer into the gaps and over the wiring lines.Problems relating to moisture absorption, spin-on-glass outgassing andincomplete gap fill in small geometries are observed and are likely tobecome more problematic for further reductions in device size. Thus, itwould be desirable to provide a method for filling small geometry, highaspect-ratio gaps with a dense, high quality dielectric material.

SUMMARY OF THE PREFERRED EMBODIMENTS

One aspect of the present invention provides a method of making asemiconductor device isolation structure in which a high density plasmachemical vapor deposition (HDPCVD) process is utilized. Preferably, thedeposition process is controlled to both optimize gap filling speed andto protect structures on the device from etching carried out during thedeposition process or in other processes.

Certain embodiments of the present invention include a method forforming over a substrate wiring line structures separated by gaps. Themethod includes providing a substrate and a wiring line layer above thesubstrate. A first antireflective coating is formed on the wiring linelayer. A second antireflective coating is formed on the firstantireflective coating, wherein the first antireflective coating and thesecond antireflective coating are formed from different materials.Portions of the first antireflective coating, the second antireflectivecoating, and the wiring line layer are etched to form wiring linesseparated by gaps, and a dielectric material is deposited within thegaps between the wiring lines.

Embodiments of the present invention also include a method for formingconducting structures separated by gaps on a substrate. The methodincludes providing a substrate and a wiring line layer above thesubstrate. A cap layer is formed above the wiring line layer. A portionof the cap layer and a portion of the wiring line layer are etchedthrough to form wiring lines separated by gaps, the wiring lines havinga remaining portion of the cap layer thereon. A dielectric material isdeposited within the gaps using high density plasma chemical vapordeposition at a sputtering rate sufficient to fill the gaps.

Additional embodiments also include a method for forming conductingstructures separated by gaps filled with dielectric material. A surfacelayer is formed over a surface of a silicon substrate, the surface layercomprising at least one material selected from the group consisting oftitanium nitride, titanium silicide and a titanium-tungsten alloy. Ametal wiring layer is formed on the surface layer, the metal wiringlayer having an upper surface. A protective layer having a top surfaceis formed on the upper surface of the metal wiring layer, the protectivelayer comprising at least one material selected from the groupconsisting of titanium nitride, titanium silicide and atitanium-tungsten alloy. A cap layer is formed on the top surface of theprotective layer, the cap layer comprising at least one materialselected from the group consisting of an oxide, a nitride, and anoxynitride. A patterned photoresist layer is formed above the cap layer,the patterned photoresist layer covering selected portions of the caplayer and exposing other portions of the cap layer. Exposed portions ofthe cap layer, the protective layer, and the metal layer are etched toform wiring lines separated by gaps. A layer of high density plasmachemical vapor deposition dielectric material is formed within the gaps.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are described with reference to theaccompanying drawings which, for illustrative purposes, are schematicand are not drawn to scale, where:

FIGS. 1-4 illustrate the processing steps in the formation of anintegrated circuit device including the formation of a cap layer and theformation of a gap between conducting structures according toembodiments of the present invention.

FIGS. 5-8 illustrate the formation of a cap layer according toembodiments of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As devices are scaled to smaller geometries, precise alignment ofmasking layers and precise control of etching processes are necessary toensure proper device function and to minimize defect formation. Defectsin photoresist masking layers may occur when reflections from underlyinglayers expose portions of the photoresist layer in an unintended manner.Unintended exposure of the photoresist etch mask can produce wiring linepatterns that exhibit unacceptable levels of variation in wiring linethickness and unacceptable wiring line failure rates. In addition,conventional CVD techniques cannot adequately fill the high aspect ratiogaps between conducting structures (such as wiring lines) on a substratesurface. Conventional techniques such as PECVD tend to deposit materialin a manner so that voids become enclosed within the gaps between thewiring lines. Such voids may be uncovered during subsequent processingand may indirectly result in decreased device performance.

Preferred embodiments of the present invention utilize a process forforming wiring lines using multiple masking and other layers and a twostep etching process. The gaps between the wiring lines arc preferablyfilled with a dielectric material deposited using high density plasmachemical vapor deposition (HDPCVD). HDPCVD allows for the addition of asputter component to the dielectric deposition process, which can becontrolled to promote gap-filling during deposition, achieving gap fillresults superior to conventional CVD processes. The sputter componentacts to remove dielectric material from areas near the top of the wiringlines which tends to then be redeposited within the gap. The multiplelayers from which the wiring lines are formed may include a cap layer, aprotective coating layer, a metal layer and a glue layer disposed overthe substrate. The cap layer may serve a number of functions, acting asan antireflective coating, a hard mask for metal line etching, and aprotector for the top corners of metal wiring lines during the HDPCVDprocess.

High density plasma chemical vapor deposition (HDPCVD) systems have beendeveloped which arc capable of providing high quality dielectric layersat deposition temperatures significantly reduced from conventional CVDof dielectric layers. HDPCVD systems are commercially available (forexample, from Novellus Systems, Inc.), which deposit a dielectric layerhaving superior density, moisture resistance and planarizationproperties as compared to conventional CVD dielectric layers. The highdensity plasma, which mediates deposition in HDPCVD systems, may begenerated from a variety of sources such as electron cyclotronresonance, inductively coupled plasma, helicon, and electrostaticallyshielded radio frequency. All of these plasma generation mechanismsallow for the addition and independent control of a bias sputtercomponent to the deposition process. Manipulating the relative substratebias can alter the deposition conditions, altering the energy of the CVDprecursor gases and the extent to which etching and sputtering processesoccur during deposition. Control of the substrate bias makes it possibleto achieve substantially void-free gap filling with enhancedplanarization in an intermetal dielectric deposition process. The biassputter component provides an etching component to the depositionprocess which can be controlled to remove or prevent the build-up ofdielectric material deposited on the upper portions of the wiring linesidewalls during gap fill. Such a build-up is observed when otherdeposition methods such as PECVD are used to fill small gaps withoxides. Formation of such build-up on the sidewalls of wiring lines canlead to the inclusion of voids in the intermetal dielectric material.Eliminating such air-filled voids is desirable to reduce the impact thatvoids in intermetal dielectrics can have on future processing.

The bias sputtering component of HDPCVD derives from the introduction ofan accelerating potential between the plasma-excited deposition gasesand the deposition substrate. Such an acceleration potential may arisedifferently in different geometry systems. Commonly, part of theacceleration potential derives from the dc self-bias effect whereby asubstrate held at a fixed potential develops a self-bias with respect toan adjacent plasma. The level of dc acceleration potential can be variedby varying the potential to which the substrate is tied. In most HDPCVDsystems, an additional, independently variable rf bias is typicallyprovided between one or more plates and the substrate. This independentrf bias allows for more complete control of the accelerating bias andthe sputtering rate and helps to prevent the uneven charge build-uppossible in a purely self-biased system.

The ions accelerated through the bias sputter component of HDPCVDprocesses etch the material present on the surface of the depositionsubstrate and sputter the etched material so that it is redeposited,generally on more recessed portions (i.e., farther from the ion flux) ofthe substrate. As an oxide is deposited onto the surface of a substratein a HDPCVD process incorporating bias sputtering, the oxide is alsoetched from the surface of the substrate and sputtered into recessedportions of the substrate. Typically, the ions that are most prevalentin the bias sputtering process are relatively inert argon ions, socomparatively little of the process proceeds through chemical mechanismsand the process primarily proceeds through a physical transportmechanism. The etch rate of oxide HDPCVD processes varies as a functionof the angle of incidence of the etching ions, with normally incidentions etching at a slower rate than ions that are incident at higherangles. The effect of this angular dependence of the bias sputtercomponent of HDPCVD is that the edges of structures are etched at afaster rate than the central portions of the structures. As such, thoseportions of a deposited layer that are closest to a gap are the mostlikely to be etched and sputtered into the gap. This produces surfacefaceting of the HDPCVD process and the ability of the process to fillgaps effectively. It should be recognized that any plasma based processcan exhibit sputter etching and deposition mechanisms. When the presentinventors discuss sputtering rates in HDPCVD processes, the presentinventors intend to convey a sputtering rate in comparison to a baseline level of sputtering characteristic of a process such as PECVD.

Another advantage of the use of HDPCVD to deposit intermetal dielectricsis that it is generally not necessary to perform subsequent hightemperature densification steps to densify the deposited dielectricmaterial, which may sometimes be required to densify oxide layersdeposited using conventional CVD and other techniques. Use of HDPCVDprocesses desirably reduces the number of process steps for making adevice and minimizes exposure of the device to elevated temperatures.

HDPCVD processes may accomplish both deposition and etching at the sametime, depending on the level of bias sputter component chosen for thedeposition environment during the process. Bias sputtering removes andredistributes dielectric material from wiring line sidewalls and enablessubstantially void-free filling of gaps and enhances planarization. Asdescribed above, the sputter component acts to prevent material build-upat the comers of the wiring lines and results in better gap-filling. Itshould be noted that an excessive etching component during HDPCVDdielectric deposition may damage either wiring lines or one or more ofthe protective layers that might be provided over the wiring lines.Thus, the sputter component is preferably controlled or other processcharacteristics are adjusted to protect the wiring lines and desiredportions of the intermetal dielectric. Favorable gap-filling withprotection of the wiring lines can be accomplished by forming a cappinglayer above the wiring lines for protection and then performing anHDPCVD step to deposit material within the gaps, with the HDPCVD steppreferably carried out at a high etch to deposition rate. The cap layermay be sacrificially etched during the HDPCVD processing and protectsthe underlying metal wiring line from undesirable etching during thedielectric deposition process. Appropriate selection of the cap materialand of the shape of the cap layer formed over individual wiring linescan be used to tailor the deposition processes in addition to protectingthe metal wiring lines from undesirable etching.

It should be appreciated that, while the present invention is describedwith reference to a particularly preferred embodiment in which the caplayer is formed and then the HDPCVD step is carried out at a high etchto deposition rate, variations on this process may be desirable. Forexample, the presently preferred embodiments utilize oxides for theHDPCVD layer, but it would be possible to utilize other materials ifappropriate deposition techniques were available. Preferred embodimentsof the present invention are now described with reference to FIGS. 1-7.FIG. 1 shows a cross-sectional view of a semiconductor substrate 20having a number of layers deposited thereon for the formation of wiringlines. The substrate may contain a variety of elements, including, forexample, transistors, diodes, and other semiconductor elements (notshown) as are well known in the art. The substrate 20 may also includeother metal interconnect layers.

As seen in FIG. 1, surface layer 22 is deposited on the substrate,followed by wiring line layer 24. If portions of the surface of thesubstrate 20 which will make contact with the wiring lines are siliconand the wiring line layer 24 is aluminum, then surface layer 22 maycomprise a material such as titanium nitride, titanium-silicide, or atitanium-tungsten alloy. Surface layer 22 acts as a barrier to preventinteractions such as interdiffusion between the silicon and thealuminum. The surface layer 22 may also help adhere the wiring linelayer 24 to the substrate 20, particularly when the wiring line isformed on a dielectric layer, and may reduce electromigration tendenciesin the aluminum wiring lines. The wiring line layer 24 may be formedfrom a variety of materials, such as aluminum, aluminum alloyed withsilicon or copper, copper, alloys including copper and multilayerstructures including comparatively inexpensive metals and more expensivemetals such as the refractory metals. Protective layer 26 is depositedon the wiring line layer 24. Protective layer 26 may be the samematerial that makes up surface layer 22. The protective layer 26 servesseveral functions, including protecting the wiring line layer 24,limiting electromigration, providing more reproducible contacts andacting as an antireflective coating over the wiring line layer 24 andbelow a layer of photoresist by absorbing light transmitted during theexposure of the photoresist to light. When layer 26 is used as part ofan antireflection coating on the wiring line layer 24, it is preferablethat the layer 26 be highly conductive, provide stable ohmic contacts toa variety of metals, and to be absorptive at the wavelength used toexpose the photoresist layer during formation of the etch mask. As such,titanium nitride is a particularly preferred material for the layer 26.The thickness of layer 26 is typically on the order of one to a fewhundred angstroms. It is possible to provide a thickness for layer 26that would cause the layer 26 to act as a quarter waveplate at theexposure wavelength. This is generally not preferred. Rather, it ispreferred that the titanium nitride layer 26 be only a part of anantireflection coating for the patterning of wiring line layer 24.

Cap layer 28, which is preferably formed from silicon oxide, siliconnitride or oxynitride, is deposited over the protective layer 26. Ifsilicon oxide is used for cap layer 28, then it is preferred that asilicon rich oxide (SRO, SiO_(2-x)), i.e., a silicon oxide having agreater concentration of silicon than is stoichiometric for silicondioxide, be used to provide a harder oxide layer. Next, a layer ofphotoresist is provided over the cap layer 28 and the photoresist isshaped to form an etching mask 30 so that the surface of cap layer 28 isexposed at regions 32 where trenches will be formed by etching andwiring lines defined. The cap layer 28 may then be etched to complete ahard mask for etching. Alternatively, the photoresist layer itself maybe used as the mask for etching layers 28, 26, 24 and 22, since this isa simpler process.

The wiring lines are formed by consecutively etching layers 28, 26, 24and 22 from the surface of the substrate 20 in order to form gaps 36between the wiring lines. A small portion of the substrate 20 may beetched as well. The etch processes used to remove these layers arepreferable highly anisotropic and may, for example, be performed byreactive ion etching (RIE). If silicon dioxide is used for cap layer 28,then a suitable etchant may be derived from a mixture of gases thatincludes CF₄, C₂ F₆, or C₃ F₈. A suitable etchant for the protectivelayer 26, metal line layer 24 and surface layer 22 may be derived from amixture of gases that includes HCl, Cl₂, or Cl₂ and BCl₃.

The cap layer 28 may serve a number of functions. During the exposure ofthe photoresist layer to light to shape the mask prior to etching, thecap layer may be used as a quarter wave plate in order to prevent lightfrom passing through the cap layer and reflecting back up to thephotoresist layer and causing the photoresist layer to become exposed inregions that are supposed to remain unexposed. Rather than absorbinglight like the protective layer 26, the quarter wave plate createsdestructive interference to prevent light from reflecting up to thephotoresist layer. Those of ordinary skill in the art will appreciatethat the particular thickness of layer 28 to be provided when layer 28has its preferred function as a quarter wave plate is different fordifferent materials. The preferred thickness for layer 28 can bedetermined by setting the thickness to be one quarter of the wavelengthof the exposure light taking into account the dielectric constant of thematerial in layer 28 at the wavelength of the exposure light. Moregenerally, the thickness may be set so that twice the thickness of thelayer 28 is an odd number of half wavelengths of the exposure light,taking into account the dielectric constant of the material. It shouldfurther be appreciated that minor variations from the optimal thicknessof layer 28 as a quarter wave plate will typically be effective inreducing reflectivity, although less effectively. In addition to actingas a quarter wave plate, the cap layer 28 may, depending on the materialused, also act to absorb light in the same manner as the protectivelayer 26. The resulting antireflection structure has the furtheradvantage of providing a graded change in the index of refraction.Reflectivity from a boundary between materials having differentdielectric constants bears a complex relationship to the differencebetween the dielectric constants of the materials on either side of theboundary. Simplistically, however, reducing the difference between thedielectric constants of materials on either side of a boundary generallyreduces the reflection from the boundary. Providing a layer of siliconoxide or silicon nitride 28, either of which has a dielectric constantcloser to that of photoresist than titanium nitride, over the titaniumnitride layer 26 tends to reduce the reflection from the boundarybetween the titanium nitride layer 26 and the photoresist layer thatwould be expected during the exposure process if the surface layer 28were not present.

As noted above, the cap layer 28 may also be used as a hard mask forwiring line etching. In embodiments where the cap layer is used as ahard mask for wiring line etching, the etching is accomplished in a twostep process in which the photoresist layer 30 acts as a mask during thefirst etch step, and the cap layer 28 acts as a mask during the secondetch step. The first etch step etches through the portions of the caplayer that arc not covered by the photoresist. The second etch stepetches through the protective layer 26, the wiring layer 24 and thesurface layer 22. By carrying out the etching process in two steps withthe photoresist being removed prior to the second etching step, thelikelihood of contaminants, such as carbon compounds from thephotoresist layer, being deposited deep within the gaps 36 betweenwiring lines 34 is decreased. Alternatively, the etching can be carriedout in a process in which the photoresist is used as the mask foretching all of the layers. This alternative process is faster, but runsa greater risk of contamination that could adversely affect deviceperformance.

In addition, the cap layer 28 may also act as a wiring line top cornerprotector during subsequent HDPCVD processing, which will be discussedbelow. After the etching is completed and resist layer 30 is removed,the structure includes gaps 36 located between individual wiring lines34. An HDPCVD step is then carried out to form layer 38. FIG. 3 shows anearly stage of the deposition of HDPCVD layer 38, which is depositedonto the surface of the substrate 20, onto the sides of the wiring lines34, the sides of the surface layer 22 and protective layer 26, and thesides and top of the cap layer 28. In certain preferred embodiments, theHDPCVD step is carried out at a sufficiently high etch to depositionratio so that the high aspect ratio gaps 36 between the wiring lineswill be filled with oxide material. The etching occurs because of thesputter component discussed above, which causes a portion of the caplayer 28 to being etched away along its sides and top surface. Thesputter biased deposition technique is observed to produce a facetedtopography on the surface of the deposited material, such as the 45°facets extending to the top of layer 38 as shown in FIG. 3.

The HDPCVD of layer 38 is performed until the gap 36 is substantiallyfilled with a material that is preferably high density oxide havingessentially no voids therein. By essentially void free the inventorsmean that when compared with a conventionally deposited oxide layer, theHDPCVD oxide layer will be substantially free of voids. As shown in FIG.4, the gap may be filled to the level of the top of protective layer 26.Depending on the subsequent processing steps to be performed, the areaabove the deposited layer 38 may next be filled with layer 40. The layer40 may be selected from a variety of materials and formed using avariety of techniques. Preferably, the layer 40 is a PECVD oxide layer,which may be deposited at a higher speed than is typical of presentHDPCVD processes. Alternatively, the deposition of HDPCVD layer 38 maybe continued so that at least a part of layer 40 is also formed in thesame step. As the deposition proceeds, the HDPCVD layer tends toself-planarize. Such a self-planarized layer requires less time forchemical mechanical processing (CMP) than a layer deposited using other,conventional techniques.

Embodiments of the present invention may also incorporate layers havingshapes different from the shape of the individual cap layers 28 shown inFIG. 2, which are rectangular in cross-section. Depending on theetchants used and the position of the mask used in patterning the layer28 into individual cap layers 28, the cap layers may have shapes such asthose shown in FIGS. 5-7. FIG. 5 shows a cross-sectional view ofindividual cap layers 48 having a triangular shape. FIG. 6 shows across-sectional view of individual cap layers 58 having a four sidedstructure with the sides extending at an inward angle from the bottom ofthe cap to the top. Cap layers 58 can also be described as trapezoidalin cross-section. FIG. 7 shows a cross-sectional view of individual caplayers 68 having rectangular shapes with their upper corner regionspartially etched away. The exact geometry of the etched away regions mayvary depending on the etchant used in forming the structure. The upperregions of the cap layers 68 shown in FIG. 7 may be formed using anisotropic etchant. FIG. 8 shows a cross-sectional view of individual caplayers 78 having rectangular shapes with their upper corner regionspartially etched away. The upper corner regions of cap layers 78 may beformed using an anisotropic etchant. Depending on the material used forthe layer (and its dielectric constant, for example), it may bedesirable to minimize the amount of the layer material that gets etchedduring the HDPCVD process and redeposited within the gap to avoidincreased capacitive coupling between adjacent wiring lines mediated bythe intermetal dielectric. As a result, a layer having inward facingsides may be preferable for certain embodiments. In addition, asdescribed earlier and shown in FIGS. 3 and 4, the cap layer may have afaceted shape after the HDPCVD step. Providing the capping layer with asimilar faceted shape (such as that shown in FIG. 8) prior to the HDPCVDshape may provide certain advantages in the process.

In another aspect of certain embodiments, the cap layer, which may notbe a conductive material, may be removed prior to an electricalconnection being made to the wiring lines.

While the present invention has been described with particular emphasison certain preferred embodiments of the present invention, the presentinvention is not limited to the particular embodiments described herein.For example, electrical isolation of components other than wiring linesmay be accomplished using techniques such as those set forth above. Thescope of the present invention is to be determined by the followingclaims.

What is claimed:
 1. A method for forming conducting structures separatedby gaps on a substrate, comprising:providing a substrate and a wiringline layer above the substrate; forming a first antireflective coatingon the wiring line layer; forming a second antireflective coating on thefirst antireflective coating, wherein the first antireflective coatingand the second antireflective coating are formed from differentmaterials; forming a mask layer above the second antireflective coating,wherein the mask layer covers selected portions of the secondantireflective coating and exposes other portions of the secondantireflective coating; etching the first antireflective coating, thesecond antireflective coating, and the wiring line layer, at thelocation where the second antireflective coating is exposed by the masklayer, to form wiring lines separated by gaps; and depositing adielectric material within the gaps to fill the gaps, using high densityplasma chemical vapor deposition.
 2. The method of claim 1, wherein thefirst antireflective coating works by absorption and the secondantireflective coating works by interference.
 3. The method of claim 1,wherein the mask layer is a patterned photoresist layer.
 4. The methodof claim 1, wherein a portion of the second antireflective coating isetched during the high density plasma chemical vapor deposition.
 5. Themethod of claim 1, further comprising the formation of a surface layerbetween the substrate and the wiring line layer, the surface layer beinga barrier between the substrate and wiring line layer.
 6. The method ofclaim 1, further comprising the step of removing the secondantireflective coating after the deposition of a dielectric materialwithin the gaps.
 7. The method of claim 1, wherein part of the secondantireflective coating is removed and remaining portions of the secondantireflective coating act as a mask during the etching of the firstantireflective coating and the wiring line layer.
 8. The method of claim1, wherein after etching each wiring line has a portion of the secondantireflection coating thereon, the portion of second antireflectioncoating on each wiring line having a cross-sectional shape selected fromthe group consisting of a rectangle, a triangle, a trapezoid, and arectangle having its upper corners etched away.
 9. A method for formingconducting structures separated by gaps on a substrate,comprising:providing a substrate and a wiring line layer above thesubstrate; forming a cap layer above the wiring line layer; forming amask layer above the cap layer, wherein the mark layer covers selectedportions of the cap layer and exposes other portions of the cap layer;etching the cap layer, and the wiring line layer, at the locations wherethe cap layer is exposed by the mask layer, to form wiring linesseparated by gaps, the wiring lines having a remaining portion of thecap layer thereon; and depositing a dielectric material within the gapsat a sputtering rate sufficient to fill the gaps, using high densityplasma chemical vapor deposition.
 10. The method of claim 9, wherein thecap layer is used as a hard mask during etching of the wiring linelayer.
 11. The method of claim 9, wherein the cap layer is anantireflective coating.
 12. The method of claim 9, wherein the remainingportion of the cap layer is partially etched during the deposition of adielectric material using high density plasma chemical vapor deposition.13. The method of claim 9, wherein the cap layer comprises a materialselected from the group consisting of a silicon nitride material and anoxynitride material.
 14. The method of claim 9, wherein the remainingportion of the cap layer on at least one wiring line has a rectangularshape in cross section.
 15. The method of claim 9, wherein the remainingportion of the cap layer on at least one wiring line has a trapezoidalshape in cross section.
 16. The method of claim 15, wherein thetrapezoidal shape includes top and bottom surfaces parallel to oneanother and side surfaces that extend inwardly from the bottom surfaceto the top surface.
 17. The method of claim 9, wherein the remainingportion of the cap layer on at least one wiring line has a triangularshape in cross section.
 18. The method of claim 9, wherein the remainingportion of the cap layer on at least one wiring line has, in crosssection, a rectangular shape having its upper comers etched away. 19.The method of claim 9, wherein the remaining portion of the cap layer ispartially etched and redeposited into the gaps during the high densityplasma chemical vapor deposition process.
 20. The method of claim 9,wherein the mask layer is a patterned photoresist layer.
 21. A methodfor forming conducting structures separated by gaps filled withdielectric material, comprising the steps of:providing a substratecontaining silicon, the substrate having a surface; forming a surfacelayer comprising at least one material selected from the groupconsisting of titanium nitride, titanium suicide and a titanium-tungstenalloy, the surface layer disposed on the substrate surface; forming ametal wiring layer on the surface layer, the metal wiring layer havingan upper surface; forming a protective layer comprising at least onematerial selected from the group consisting of titanium nitride,titanium silicide and a titanium-tungsten alloy, the protective layerdisposed on the upper surface of the metal wiring layer, the protectivelayer having a top surface; forming a cap layer comprising at least onematerial selected from the group consisting of an oxide, a nitride, andan oxynitride, the cap layer disposed on the top surface of theprotective layer; forming a patterned photoresist layer above the caplayer, said patterned photoresist layer covering selected portions ofthe cap layer and exposing other portions of the cap layer; etching theexposed portions of the cap layer, the protective layer and the metallayer to form wiring lines separated by gaps; and forming a layer ofhigh density plasma chemical vapor deposition dielectric material withinthe gaps to fill the gaps.